[gedikk]

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IMPs at a BBO table. N-S play 2/1 with 5533 openings and strong reverses.
E-W are adhoc opps and their bidding not in my focus. Much more interested in your assessment and methods sitting N-S - up to the second double and beyond.

[rmnka447]

A 5-4-2-2 is referred to as a semi-balanced hand. Sometimes such a hand is treated as balanced and sometimes as unbalanced. Here with most of the points concentrated in the long suits, there's no problem treating the hand as more "unbalanced" and opening 1 ♦. Had the hand been something like ♠ K10xx ♥ AJ ♦ Kxxxx ♣ AQ, North should strongly consider treating it as balanced and opening with a strong 1NT.

There is no problem with the rest of the North/South auction through the opponent's second double. Note that the 1 ♠ rebid by North can be on a hand up to about 18 HCP. However, it could also still be on minimum opening values. At this point there's just no way for South to know.

If North holds only 4 ♠, which is very likely, then there is a possibility that the second double might be passed out and converted to a penalty double. That can be disastrous holding only 5 trump total between the two hands. With a stiff ♦, preferencing back to 2 ♦
doesn't look any more attractive.

Let's consider South's hand. It does have two suits, but the hand is a minimum response in terms of HCP. From the bidding so far, the hand appears to be a misfit with the North hand. Since passing is not an option, South should simply rebid 2 ♥ which shows long ♥ and not much else.

With 2 ♥ honors and extra points, North might raise to 3 ♥. Then South would bid on to 4 ♥.